Process for the preparation of fluosulfonates



United States Patent Ofiice 3,083,220 Patented Mar. 26, 1963 3,083,220 PRQCESS FOR THE PREPARATIQN F FLUOSULEONATES William Lee Edens, New Castle, Del., assiguor to E. L du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware No Drawing. Filed July 3, 1958, Ser. No. 746,345 5 Claims. (Cl. 260-456) wherein R is a member of the class consisting of fluorine, perfiuoroalkyl groups and omega-hydroperfiuoroalkyl groups. The novel fiuosulfonates are prepared by the reaction of concentrated sulfuric acid with a fluorinated olefin having the formula RCF CF where R is as indicated above, at temperatures of 300 to 400 C., or by the reaction of fiuosulfonic acid with the periluorinated or substantially perfiuorinated olefin at temperatures of 100 to 400 C.

In contrast to completely halogenated ethylene containing more than one halogen-type such as difiuorodichloroethylene and trichlorofluoroethylene which do not form the fluosulfonates, it was found that perfluoroolefins and substantially periluorinated olefins react to form the fluosulfonates of the present invention and, surprisingly so, it was found that these compounds could be prepared by reaction of sulfuric acid with the olefin in addition to the preparation by reaction with iluosulfonic acid.

The preparation is carried out by combining the reactants and heating the mixture at elevated temperatures. No catalysts or solvents are necessary. The quantities of the reagents may be greatly varied and are in no way critical to the formation of the fluosulfonates. In general, it is preferred to react substantially equimolar quantities of the acid with the olefin. The reaction is carried out at a temperature of 300 C. to 400 C. and preferably at 350 C., when sulfuric acid is employed and at a temperature of 100 C. to 400 C., and preferably at a temperature of 150 0, when fiuosulfonic acid is employed. In general, the reaction is carried out at autog enous pressures, although higher or lower pressures may be employed if desirable.

The olefins which may be employed in the present invention are perfiuoroolefins and omega-hydroperfluoroolefins. Representative examples of these olefins suitable in the formation of the fiuosulfonates of the present invention include tetrafluoroethylene, and perfiuoroalkyl and omega hydroperfluoroalkyl substituted perfiuoroethylenes in which the alkyl groups are unsubstituted and straight chain, and contain up to 18 carbon atoms, such as perfluoropropene, perfluorobutene-l, perfiuorohexene-l, perfluoroheptene-l, perfiuorooctene-l, omegahydroperfluoroheptene-l, omegahydroperfiuorodecene-1, perfiuorododecene, perfiuoropentadecene, etc.

The process of the present invention is further illustrated by the following examples:

Example I Hexafluoropropene (150 g.) and 96% concentrated sulfuric acid (25 ml.) were charged into a platinum lined 320 ml. autoclave. The mixture was agitated for one hour at 350 C. under autogenous pressure. The light amber product was discharged, washed twice with water, dried over calcium sulfate and distilled through a 30 inch platinum spinning band column. There was obtained 37.6 g. (32%) of a clear colorless liquid product identified as p-hydroperfluoropropyl fluosulfonate having a boiling point of to 76 C., a refractive index of N =1.2865.

Analysis-Calculated for C HF O S: C, 14.4; H, 0.4; F, 53.2; S, 12.8; mol. wt. 250. Found: C, 15.5; H, 0.6; F, 52.8; S, 13.6; mol. wt. 248.

Example II Hexafluoropropene (50 g.) and fiuosulfonic acid {25 g.) were charged into a platinum lined 320 ml. autociave. The mixture was agitated for 3 hours at 150 C. under autogenous pressure. The dark amber product was poured onto ice, washed twice with water and distilled. There was obtained 11.3 g. (18%) of B-hydroperfiuoropropyl fluosulfonates boiling at 75-76 C.

Example 111 Into an evacuated 320 ml. platinum lined autoclave was charged 36 ml. of fluosulfonic acid and 70 g. of tetrafluoroethylene. The reactor was agitated for 3 hours under autogenous pressure at 200 C. The reaction products were collected in an acetone-Dry-Ice bath and. distilled. In addition to unreacted monomer there was obtained sulfur dioxide and tetrafluoroethylene dimer. The distillation heel was dropped into water and the insoluble layer resulting was separated and distilled. On distillation there was obtained 0.9 g. of B-hydroperfluoroethyl fluosulfonate having a boiling point at 56-57 C. The structure of the compound was further verified by infrared and nuclear magnetic resonance analysis.

Example I V Into a 320 ml. platinum lined autoclave was charged 11 g. of fluosulfonic acid and 20 g. of omega-hydroperfluorobutene. The reactor was agitated for 8 hours at 150 C. under autogenous pressure. Distillation of the reaction product resulted in isolation of 2.1 g. of 2,4-dihydroperfiuorobutyl fiuosulfonate, having a boiling point at 119 C.

Example V Into a 320 ml. platinum lined autoclave was charged 70 g. of perfluoroheptene-l and 15 g. of fluosulfonic acid. The reaction mixture was agitated for three hours at 150 C. under autogenous pressure. The resulting product was washed with water, sodium bicarbonate solution and again with water. The product was then filtered through anhydrous MgSO and dried over CaSO On distillation there was recovered 25 g. of unreacted olefin and 2.2 g. of ,B-hydroperfiuoroheptyl fluosulfonate having a boiling point of 53.5 to 54.5 C. at a pressure of 18 mm. Hg.

Example VI Into a 6" x platinum tube was charged 4.3 g. of omega-hydroperfiuoroctene-1 and 1.5 g. of iiuosulfonic acid. The tube was agitated for 3 hours at 200 C. under autogenous pressure. Distillation of the reaction product resulted in recovery of 2.8 g. of the olefin and isolation of 1.5 g. of 2,8-dihydroperfluorooctyl fiuosulfonate having a boiling point at to 81 C. at a pressure of 8 mm. Hg. The structure of the compounds was confirmed by infrared and nuclear magnetic resonance analysis.

Example VII Into a 320 ml. platinum lined autoclave was charged 200 ml. of fi-hydroperfluoropropyl fluosulfonate and 2 g.

of tert.-butyl peroxide. The autoclave was heated to 140 C. and pressured with 400 psi. of tetrafluoroethylene. The reaction vessel was agitated for 63 minutes at this pressure and at a temperature varying from 140 to 180 C. The reaction product was filtered and 104 g. of polytetrafiuoroethylene was isolated.

The formation of the fluosulfonates of the present invention is independent of the chain length of the fluoroalkyl radical attached to the perfluorovinyl group of the olefin and proceeds equally well with a low molecular weight fiuoroolefin as with a higher molecular weight fiuoroolefin. In general olefins having from 2 to 20 carbon atoms are employed in the formation of the novel fluosulfonate compounds of the present invention.

The fiuoroalkyl fluosulfonates of the present invention are to be distinguished from the fiuoroalkane sulfonates from which they differ in structure and properties. The fluoroalkyl groups in the fiuosulfonates are bonded to the sulfur atoms through an oxygen atom, whereas in the iluoroalkane sulfonates the fluoroalkyl group is bonded to the sulfur atom. The fluoroalkane sulfonates, furthermore, hydrolyze to fluoroalkane sulfonic acid, whereas the fluoroalkyl fiuosulfonates hydrolyze to a carboxylic acid.

The perfiuoroalkyl fluosulfonates prepared by the process of the present invention are highly valuable chemical intermediates. Thus the tluosulfonates may be employed to prepare highly fluorinated acids by base hydrolysis. The resulting Z-hydroperfluoroalkyl acids are useful as dispersing agents and may also be dehydrofiuorinated to give rise to perfitioro-a,fi-unsaturated carboxylic acids which may be employed as polymerization monomers. The perfiuoroalkyl fiuosulfonates of the present invention are furthermore useful as solvents and non-aqueous polymerization media for perfluorinated olefins, as shown by Example VII.

I claim:

1. A process for the preparation of substantially fluorinated alkyl fluosulfonates which comprises reacting an acid selected from the class consisting of sulfuric acid and fluosulfonic acid at a temperature of to 400 C., when the acid is fluosulfonic acid and 200 C. to 400 C. when the acid is sulfuric acid, with a substantially fiuorinated olefin having the formula Where R is a member of the class consisting of fluorine, perfluoroalkyl group and omega-hydroperfiuoroalkyl groups, said alkyl group being unsubstituted and straight chain and containing up to 18 carbon atoms.

2. A process for the preparation of substantially fiuorinated alkyl fiuosulfonates which comprises reacting sulfuric acid at a temperature of 200 to 400 C. with a substantially fiuorinated olefin having the formula substantially References Cited in the file of this patent UNITED STATES PATENTS 2,570,917 Calfee Oct. 9, 1951 2,628,972 Calfee et al Feb. 17, 1953 2,878,156 Davis Mar. 17, 1959 

1. A PROCESS FOR THE PREPARATION OF SUBSTANTIALLY FLUORINATED ALKYL FLUOSULFONATES WHICH COMPRISES REACTING AN ACID SELECTED FROM THE CLASS CONSISTING OF SULFURIC ACID AND FLUOSULFONIC ACID AT A TEMPERATURE OF 100 TO 400*C., WHEN THE ACID IS FLUOSULFONIC ACID AND 200*C. TO 400*C. WHEN THE ACID IS SULFURIC ACID, WITH A SUBSTANTIALLY FLUORINATED OLEFIN HAVING THE FORMULA 